1. Field of the Invention
The present invention relates to fluid catheters for transmitting light, and more particularly to fluid catheters having a low refractive index clad and aqueous fluid core.
2. Related Art
Fluid catheters for transmitting light such as laser light to a selected location for medical treatment are well known. Nath U.S. Pat. No. 3,995,934, shows a flexible light guide for transmission of visible and near infrared light, and of light from a Nd-YAG-laser. The light guide includes a tube formed from flexible plastic material and filled with a liquid sealed between the ends of the tube by a material having a high transparency for the radiation to be transmitted. The liquid has an index of refraction approximately 1/10 higher than that of the plastics material of the tube. However, because the plastics have a higher index of refraction than aqueous solutions, the light guide typically uses organic solutions. Additionally, the range of usable solutions is often limited by the type of light being transmitted through the catheter.
light transmitting fluid catheters such as fluid laser catheters are commonly used for such medical applications as ablation of lesions and the like. One common application is using laser light to dissolve thromboses or stenoses where the laser light is directed at the target to dissolve it. However, where light energy is also absorbed in the fluid through which the light passes, such as an organic based fluid in the light catheter or around the target, the laser must often be pulsed several times to avoid overheating the fluid or the catheter, or the fluid must be continually infused through the target region to prevent overheating. In some cases, the power, duration and/or frequency of light application must be varied or reduced to prevent overheating.
There is a need, therefore, for a light transmitting catheter having an aqueous core. There is also a need for light transmitting catheters that are more efficient, and therefore absorb less light energy, do not heat up as much and can accept more flexible operating parameters than previously allowed. There is also a need for a light transmitting catheter which can use an aqueous core for transmitting light and also for infusing liquid into the area of interest. There is also a need for a light transmitting catheter which can be positioned using a guide wire rather than an inflation balloon.
Liquid filled light transmitting catheters are beneficial because of their small size and their flexibility. The ability to use a liquid core light guide avoids having to use a fixed length glass fiber inside the catheter tube, thereby avoiding the decreased flexibility caused by the frictional contract between the glass fiber and the wall of the lumen in which the glass fiber is placed. Liquid core light transmitting catheters are also structurally simpler than catheters incorporating glass fiber light guides.